To obtain accurate dust opacities would require global-disc radiation-hydrodynamic simulations following the dust growth, drift, and evaporation with sufficiently high resolution both in space and in the dust size, while covering the full range of grain sizes that set the opacity, and taking the feedback of the grains on the disc structure into account. This is not yet computationally feasible. However, different studies have looked at some of these aspects (e.g. [1]}, [2]}, [3]}, [4]}, [5]}, [6]}),
with some properties emerging. We highlight briefly four of them.
